Brightwall Village Demon Door

You need only show up in front of this Demon Door with a child -- sounds easy right? Well, there's a catch: it has to be your OWN child. This is because your child is the only child you can hold hands with and, consequently, drag to the Demon Door for the Door's approval. To have a child, you must have the Family and Lover Expression Packs from the Road to Rule. Propose to a potential mate (of the opposite sex -- since you need to make a child), fulfill he or she's marriage requirements, purchase a house and have "Unsafe" sex by activating the Sleep icon at the bed your house and choosing to do so. After this you will have an infant child. Wait a bit for the child to become a toddler and you can then take it to the Demon Door.

Alternately, you may adopt a child from the Bowerstone Orphanage, which is MUCH FASTER, but you can only do this after discovering Bowerstone Industrial (and you can do it if you turn the orphanage into a brothel as Ruler of Albion; you must adopt a kid on the street near the brothel). The orphanage is in the same building where the Kidnapped Side Quest began. Walk all the way to the rear of the orphanage and make a right. Here you'll find a room full of kids in front of beds. You can adopt one for 500G. Choose a home in Brightwall and you can grab your new kid and drag him or her to the door easily.

You MUST interact with your child using Hug or another expression in front of the door to get it to open. Inside the Demon Door you'll find 25 Guild Seals and 3 Summon Creature Potions in the "Last Orders" area.